Question

The analysis of a fuel is found to have carbon 86%, hydrogen 5%, oxygen 2%, sulphur 0.5% by weight and the remainder is nitrogen.

The stoichiometric air fuel ratio is ____.

(Assume that air contains 23% $O_2$ by mass)

• A. 11.64

Answer 1

The correct option is A 11.64

Let a 1 kg sample of fuel is taken

So, 1 kg fuel contains 0.86 kg C, 0.05 kg $H_2$, 0.02 kg $O_2$ and 0.005 kg S

So, $N_2$ in 1 kg fuel = 1 – (0.86 + 0.05 + 0.02 + 0.005) = 0.065 kg

Total $O_2$ required = 2.293 + 0.4 + 0.005 = 2.698 kg

Net $O_2$ required = Total $O_2$ required - $O_2$ already present

=2.698 – 0.02 = 2.673 kg

Net air required = $\frac{2.678\times 100}{23}=11.64$ kg per kg of fuel